On Capitol Hill, staffers often find that addressing one’s boss is rarely a straightforward affair. What you call the person whose name is on the door might depend on your own seniority and your audience. Mostly, though, it depends on the bosses’ personal quirks.

It’s difficult to generalize along age, gender or regional lines about who likes to be called what. Instead, Members’ monikers are highly individual choices, in some cases a product of branding (a first name connotes an everyman humility, while “doctor” reminds voters that their lawmakers have chops on health care legislation) and others, just old habits.

Among the most distinct are the many doctors of Congress. Some of the body’s opticians, veterinarians and surgeons prefer to be identified with their first professions. No wonder there: Doctors are the fifth-most-trusted profession in Gallup’s annual survey; Members of Congress rank above only used-car salesmen and lobbyists.

Rep. Paul Broun might have the voting card of a Member of Congress, but the honorific he prefers is “doctor,” not “Congressman.” In addition to simply being the title the Georgia Republican is used to after years as a black-bag-toting house-call physician, it serves another purpose.

“In Washington, being a doctor has helped him be an influence in health care debates because he has that experience,” spokeswoman Meredith Griffanti says. The M.D. behind his name, featured prominently on his Congressional and campaign websites, is a reminder of his credentials.

Over on the Senate side, John Hart has known his boss, Sen. Tom Coburn for 14 years, and in that time, the only thing he’s called him is “Dr. Coburn.”

“None of us would ever call him ‘Tom,’” says Hart, the Oklahoma Republican’s spokesman. “His friends call him that, but in a professional capacity, it’s always ‘Dr. Coburn.’”

Coburn’s medical bona fides have lent him credibility on health care issues, but the name has sometimes been turned against him: He’s been dubbed “Dr. No” for his frequent opposition to measures he considers unconstitutional. But he clearly derives his identity from his first career, not his current one: Call the Senator’s office and a chipper voice greets you: “Dr. Coburn’s office!”

Some Members like to have their under-the-Dome status recognized. Sen. Barbara Boxer (D-Calif.) in 2009 asked a witness testifying before her to address her as “Senator,” not “ma’am.”

“I worked so hard to get that title,” she informed the witness.

Many Members prefer a more casual approach and ask that everyone, from their interns to their constituents, call them by their first names. First names appear to be more prevalent in the House than in the more-formal Senate, and younger Members seem to use them more often — though it’s hardly the exclusive province of the junior set.

Rep. Rosa DeLauro says she appreciates that people she meets, including constituents or new staffers, want to show respect by calling her “Congresswoman.” But, the Connecticut Democrat says, that’s not her name. “I’m just Rosa.”

DeLauro thinks being on a first-name basis puts people at ease. “The issue is to not create distance, and you want people to know, genuinely, that you’re accessible,” she says. “We don’t live in two different worlds. I happen to serve in this body, and they do what they do.”

And Sen. Sherrod Brown is “Sherrod” wherever he goes. That level of informality is relatively rare in a Senate office, and it took Meghan Dubyak, spokeswoman to the Ohio Democrat, awhile to adjust. “I found myself calling him ‘Senator,’” she says. “And he’d reply by calling me ‘press secretary.’ He’s generally very down-to-earth — which extends to his office.”

Meredith Persily Lamel, a consultant who works with Congressional offices, says whether the boss goes by “John” or “Chairman,” the important thing is to keep the monikers consistent. She thinks it’s difficult for staffers to talk to colleagues about their boss using his first name, then in the next breath take a constituent call in which they call him “Congressman Smith,” for example.

“Eventually, they’re going to slip, and that’s where consistency is helpful,” she says.

That’s why more senior staffers often call the boss by his or her first name and junior staffers use a more formal address.

Senior staffers, Lamel says, are better able to adjust the name to the situation — and they just have more practice switching gears.

Lamel says Members’ choices of what they want their staff to call them is personal and that a casual tone doesn’t mean a lack of reverence for the Member or the institution.

“Some of the offices I work with where the Member goes by a first name are those where staffers have the greatest respect and the most interest in the boss’s approval.”

But some say informality has its downside. In an era where Hill staffers wield quite a bit of power — thanks to bosses with plenty on their plates and a healthy dependence on delegating — a title still sends a powerful message.

“I think it’s generally good for staff to be reminded that they’re staff, not Members,” one Senate aide says. “It can be easy to substitute your own judgment for your boss’s.”

Doug McCann, a longtime Hill staffer who now teaches Congressional affairs at the University of Maryland and Georgetown University, says a level of formality is healthy.

“It helps remind us that there are only 535 people with those little badges,” he says. “The rest of us are just hired help.”

And no matter where on the matter their own boss stands, staffers agree that when addressing a Member who’s not their boss, formality always rules. In elevators, in the hallways or in meetings, the most respectful address seems to be the default position.

“It’s always ‘Congressman,’ or ‘Congresswoman,’ no question,” one GOP House staffer says. “You always remember that you’re representing your boss, but that doesn’t mean that you’re as familiar as your boss is with his colleagues.”

Even once one has sorted out who likes to be called what, there’s the not-so-small matter of what to call them in writing. A first name might not be appropriate, but using only a last name might sound brusque or disrespectful. And so in internal emails and texts, many staffers refer to the boss by his or her initials.

The phenomenon persists even for Members whose middle names aren’t often invoked. Coburn, for example, is usually “TAC,” short for Thomas Allen Coburn, in his staff’s internal communications.

“That’s shorthand,” Lamel says. “It’s a respectful way to save a few keystrokes.”

In fact, some staffers so frequently type out initials that they begin using them in conversations, adding another name into the already jumbled pile of Hill names.

Titles can be tricky, too. Some female Members, including Boxer, like to use “Chairman” instead of “Chairwoman.” Rep. Marsha Blackburn (R-Tenn.) identifies herself as “Congressman.”

If it’s a confusing maze to navigate, there’s one surefire trick to addressing a Member of Congress. McCann often offers this tip to his students, paraphrasing a quote from Harley Dirks, a powerful appropriations clerk during the 1960s: “I call them all ‘Chairman,’” Dirks said. “If they are, they expect it, and if they’re not, they’re flattered.”